Stdlib: Zend builtin interfaces — interface_exists()/get_declared_interfaces() must include UnitEnum, BackedEnum, ArrayAccess, Serializable (zend_interfaces.c)

[PurHur]

Category

stdlib · language

Problem

Zend registers internal interfaces (UnitEnum, BackedEnum, ArrayAccess, Serializable, …) in the class table. interface_exists() and get_declared_interfaces() must return them even though user code never declared them.

This compiler only scans user-declared interfaces in VmReflection::interfaceExists() / declaredInterfacesTable() (ext/standard/VmReflection.php). Builtin interfaces are missing:

Check	Zend PHP 8.2+	bin/vm.php today
interface_exists('UnitEnum')	true	false
interface_exists('BackedEnum')	true	false
interface_exists('ArrayAccess')	true	false
interface_exists('Serializable')	true	false
in_array('UnitEnum', get_declared_interfaces(), true)	true	false
is_a($enumCase, UnitEnum::class)	true	fatal: Unknown class for constant fetch: UnitEnum

instanceof on enum cases for builtin interfaces was fixed in #5711 (closed), but reflection builtins and UnitEnum::class constant fetch still fail — blocking generic enum utilities and self-host code that introspects enums.

php-src reference

• php/php-src Zend/zend_interfaces.c — zend_register_internal_interface, UnitEnum, BackedEnum, ArrayAccess, Serializable
• php/php-src ext/standard/basic_functions.c — PHP_FUNCTION(interface_exists), get_declared_interfaces
• php/php-src ext/standard/class.c — is_a(), is_subclass_of() with internal interfaces
• php/php-src Zend/zend_enum.c — enum case instanceof builtin interfaces

Repro

Save as test/repro/parity_builtin_interface_registry.php:

<?php
enum E: string { case A = 'a'; }
$c = E::A;

foreach (['UnitEnum', 'BackedEnum', 'ArrayAccess', 'Serializable'] as $iface) {
    echo "interface_exists($iface): ", var_export(interface_exists($iface), true), "\n";
}
echo "declared UnitEnum: ", var_export(in_array('UnitEnum', get_declared_interfaces(), true), true), "\n";
echo "is_a case UnitEnum: ";
try {
    var_export(is_a($c, UnitEnum::class));
} catch (Throwable $e) {
    echo get_class($e), ': ', $e->getMessage();
}
echo "\n";

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/repro/parity_builtin_interface_registry.php
php bin/vm.php test/repro/parity_builtin_interface_registry.php 2>&1 | grep -v listSpreadRhs
'

Scope (this repo)

Area	Path
Registry	lib/VM/BuiltinInterfaces.php (new) — seed internal ClassEntry rows at VM init
Enum parity	lib/VM/EnumSupport.php — ensure enum cases satisfy instanceof builtin interfaces (regression guard for #5711)
Stdlib	ext/standard/VmReflection.php — interfaceExists(), declaredInterfacesTable() include builtins
Constant fetch	lib/VM.php / class table — resolve UnitEnum::class, BackedEnum::class for is_a() / is_subclass_of()
JIT	ext/standard/JitInterfaceExists.php, lib/JIT/ReflectionBuiltinHelper.php — literal builtin interface names
Tests	test/compliance/cases/stdlib/builtin_interface_exists.phpt, test/compliance/cases/language/enum_is_a_unit_enum.phpt

PHP-in-PHP: register builtins in PHP (lib/VM/), not new C tables in runtime/.

Done when

• Repro: all four interface_exists() lines print true on VM
• get_declared_interfaces() includes UnitEnum and BackedEnum
• is_a(E::A, UnitEnum::class) prints true (no constant-fetch fatal)
• ./script/ci-fast.sh --filter builtin_interface green
• Distinct from Stdlib: is_subclass_of() on enum cases — UnitEnum/BackedEnum must be true (ext/standard/class.c) #5642 / Stdlib: class_implements() on enum must return UnitEnum/BackedEnum (ext/standard/basic_functions.c) #5422 (enum-case class_implements / is_subclass_of behavior on user enums)

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter builtin_interface'

Links

• Language: enum case instanceof UnitEnum/BackedEnum — must be true (zend_enum.c) #5711 (closed instanceof) · Stdlib: class_implements() on enum must return UnitEnum/BackedEnum (ext/standard/basic_functions.c) #5422 class_implements enum · Stdlib: is_subclass_of() on enum cases — UnitEnum/BackedEnum must be true (ext/standard/class.c) #5642 is_subclass_of enum · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

claim: PHP Compiler STD Lib — starting this run

[PurHur]

Merged via #7692.

Verification: VM/JIT repro prints all four interface_exists() true, get_declared_interfaces() includes UnitEnum, is_a(E::A, UnitEnum::class) true. PHPUnit --filter builtin_interface: OK (4 tests). AOT -l lint green on probe + enum_instanceof.php.

Implementation: lib/VM/BuiltinClasses.php registers UnitEnum/BackedEnum/Serializable; JIT seeds in Object_.php. No C runtime changes.